My kids loved IOA and Universal Studios! Last trip they were ages 5 + 10. We're going at the end of this month too! My now 12 year old is a defenite big coaster chicken but loves simulator type rides (spiderman).
At ISLAND OF ADVENTURE there is:
All of Seuss Land with it's rides and street show,
Lost Continent has the talking fountain (just a regular fountain but it's very humorous), The Sinbad show: very funny corny stunt type show;has some loud bangs.
Jurrassic Park has the Unicorn Rollercoaster (bigger than a kiddie coaster but still small, not sure of min heighth), Discovery Center, and Camp discovery (a play area with caves and bridges, cool; my kids LOVE play areas). Also in that area is a ride call (SP?) Pteranadon flyers but it is not worth a long wait, because the ride itself is so short. There is also the Jurassic Park ride which is a very cool ride but my has a huge hill at the end.
Toon Lagoon: Me ship, the Olive is a interactive play area and this whole area has some eye popping colors most kids really enjoy. I believe this area has a stadium show and defenitely a toon trolley street show. the characters sing and dance and sign autographs or pose for pictures. There are really fun photo ops here!
Marvel Super Hero: There are characters on the street (on and off) like Spiderman,Dr Doom, Captain America, etc. There is a tea cup like ride here call Storm Force (right now this ride appears to only be open on weekends).
I think your girls would have fun! Have a great time!